More than 50,000 people have urged Barack Obama to escalate the diplomatic feud that led Moscow to propose a law barring Americans from adopting Russian children.

Two petitions on the White House website are asking for sanctions against Russian politicians who backed a bill that one of the documents says will "jeopardise lives and well-being of thousands of Russian orphans".

Moscow sees the ban on adoptions as retaliation for a US human rights law that allows the seizure of assets from Russian officials implicated in the 2009 death of a Russian lawyer.

Some Russian politicians denounced the petitions, saying any further action would cause tensions between the countries.

Image:President Obama is under pressure to get tough with Russia

However a senior member of the Duma - Russia's lower parliamentary chamber - suggested there might still be a way for the measures to be softened.

One petition said Russian politicians "breached all imaginable boundaries of humanity, responsibility, or common sense and chose to jeopardise lives and well-being of thousands of Russian orphans".

The petitioners urged the president to "identify those involved in adopting such legislature responsible under the Magnitsky Act".

A second petition asks that the Magnitsky Act "be extended to supporters of this law in (the) Russian Duma".

According to White House rules, an official response will be issued if a petition reaches 25,000 signatures within 30 days. One already has more than 45,000 signatures, while the other has 6,000.